UNITED NATIONS, April 23 (Reuters) - Syria declared on Wednesday that it was looking ahead to the dismantling of the international mission overseeing the destruction of the conflict-torn country's chemical arsenal, though Western officials said they want the team to keep working.

The statement came after Sigrid Kaag, head of the joint mission of the United Nations and the Organization for the Prohibition of Chemical Weapons (OPCW), told the Security Council that the Syrian government should be able to meet an April 27 deadline to hand over all declared chemical agents.

Inside the council chamber, however, U.S. and European delegations told Kaag they were concerned about new allegations that Syria's government had deployed chlorine gas and expressed their view that a full investigation was necessary, diplomats said.

After the closed-door session, in which Kaag participated via video link, Syria's U.N. Ambassador Bashar Ja'afari was asked what should happen to the U.N.-OPCW mission once declared materials linked to Syrian chemical weapons had been shipped out of the country and all installations were shut down.

"Once this mission is finished, you will hear about a final report submitted by Mrs. Kaag to the council and to the executive board of the OPCW, and that will be the end of everything," Ja'afari said.

"We will act accordingly after that as a full-fledged member of the CWC (Chemical Weapons Convention)," he said.

British Ambassador Mark Lyall Grant said in an interview that he sees the U.N.-OPCW mission remaining in place for the foreseeable future due to concerns about the completeness of Syria's disclosure of its chemical arsenal.

"Our view is that there is a continuing role for the joint mission well beyond the removal of the chemicals, which could happen quite quickly now, and there's a number of tasks that are still to be carried out, including verification of the destruction of production facilities," Lyall Grant said.

"That means that the joint mission should continue," he added, noting that the Security Council decision to establish the mission did not give a deadline for its termination. Russia would therefore be unable to shut down the mission, even if it wanted to, Lyall Grant said.

"Further review and verification of Syria's declaration of its CW program is required in order for there to be international confidence that the program has been completely eliminated," a U.S. official said.

AMBIGUITIES

Western diplomats in New York have said a diplomatic battle is looming between Syria and Russia on the one hand and the West on the other over the continued role of the U.N.-OPCW mission in Syria once the declared chemicals are gone. Russia has been the Syrian government's protector on the Security Council.

The OPCW has said that nearly 90 percent of the chemicals used to produce poison gas are out of the country, a figure that may soon reach 100 percent.

Lyall Grant, like other Western delegates in New York, sees Kaag's mission continuing. "We think that it should continue to report to the council things like the ambiguities in the original (chemical weapons) declaration are examined," he said.

Similarly, the U.S. official said, "It remains to be seen how accurate the regime's declarations are."

He added that allegations about the recent use of chlorine gas highlighted the importance of keeping the mission alive.

Attacks this month in several areas of the country share characteristics that have led analysts to believe that there is a coordinated chlorine campaign, with growing evidence that it is the pro-government side dropping the bombs.

Nigerian Ambassador Joy Ogwu, president of the Security Council this month, summed up the views of council members after the meeting on Syria and Kaag's briefing.

"Council members expressed grave concern about alleged reports of the use of chlorine gas in some towns which left people dead and injured and called for an investigation of this incident," she said.

It was not clear who would carry out the investigation. Ogwu said having the U.N.-OPCW mission investigate the chlorine gas allegations was a possibility, but it was not the only option.

According to one diplomat inside the meeting, French Ambassador Gerard Araud said "reports of use of chlorine by the Syrian regime show that the full evacuation of CW by the joint mission will not put an end to the use of CW by the regime."

The diplomat said that U.S. Ambassador Samantha Power had told Kaag "it would be horrific and ironic if the regime would turn to using chlorine, which is not being removed by your mission."

Chlorine, a so-called dual-use chemical that has industrial uses, is not on the list of chemical weapons submitted to the OPCW but it was produced in Syria before the war. It should have been declared if the government has it, an OPCW spokesman said.

Ja'afari said it was not clear if chlorine gas was used in any attacks, though he said if it had been used, the rebels would be responsible. Syria and the opposition have long accused each of responsibility for all poison gas attacks.

President Bashar al-Assad agreed with the United States and Russia to dispose of his chemical weapons, an arsenal that Damascus had never previously formally acknowledged, after hundreds of people were killed in a sarin gas attack on the outskirts of the capital last August.

Washington and its Western allies have said it was Assad's forces who unleashed the nerve agent in the world's worst chemical attack in a quarter century. The government blamed the rebel side in Syria's civil war, which is now in its fourth year. (Additional reporting by Mirjam Donath; Editing by G Crosse, Toni Reinhold)